The present invention relates to a device and method for scanning of barcodes.
Present day barcode scanning is ubiquitous for stock control, and is used in shops and supermarkets, as well as in warehouses and in offices.
To quote from Wikipedia, a barcode reader (or barcode scanner) is an electronic device for reading printed barcodes. Like a flatbed scanner, it consists of a light source, a lens and a light sensor translating optical impulses into electrical ones. Additionally, nearly all barcode readers contain decoder circuitry analyzing the barcode's image data provided by the sensor and sending the barcode's content to the scanner's output port.
Barcode scanners may include laser scanners, for example solid state or semiconductor lasers including diode lasers. Alternative scanners may include CCD scanners. As a further alternative, cameras, such as mobile telephone cameras, are able to read barcodes when provided with suitable software.
Scanning methods are distinguished by the amount of operator manipulation required. Thus pen or wand-type readers require the operator to swipe the pen over the code. Semi-automatic handheld readers do not require the operator to swipe, but they must at least position the reader near the label. Fix-mount readers for automatic reading work by laterally passing the label over the reader. No operator is required, but the position of the code target must coincide with the imaging capability of the reader. Using reader gates for automatic scanning, the position of the code must be just under the gate for short time, enabling the scanner sweep to capture the code target successfully.
Pen-type readers consist of a light source and a photodiode that are placed next to each other in the tip of a pen or wand. To read a bar code, the tip of the pen moves across the bars in a steady motion. The photodiode measures the intensity of the light reflected back from the light source and generates a waveform that is used to measure the widths of the bars and spaces in the bar code. Dark bars in the bar code absorb light and white spaces reflect light so that the voltage waveform generated by the photo diode is a representation of the bar and space pattern in the bar code. The waveform is decoded by the scanner in a manner similar to the way Morse code dots and dashes are decoded.
Other types of wand are known that do not require contact with the barcode.
Laser scanners work the same way as pen type readers except that they use a laser beam as the light source and typically employ either a reciprocating mirror or a rotating prism to scan the laser beam back and forth across the bar code. As with the pen type reader, a photodiode is used to measure the intensity of the light reflected back from the bar code. In both pen readers and laser scanners, the light emitted by the reader is rapidly varied in brightness with a data pattern and the photodiode receive circuitry is designed to detect only signals with the same modulated pattern.
CCD readers use an array of hundreds of tiny light sensors lined up in a row in the head of the reader. CCD readers may have difficulty reading poorly presented barcodes, say barcodes at awkward angles or slightly damaged or covered in dirt.
Omni-directional scanners almost all use a laser. Unlike the simpler single-line laser scanners, they produce a pattern of beams in varying orientations allowing them to read barcodes presented at different angles. Most of them use a single rotating polygonal mirror and an arrangement of several fixed mirrors to generate their complex scan patterns. Omni-directional scanners are most familiar through the scanners with two scanning windows that are widely used in supermarkets, where packages are slid across a glass or sapphire window. There are a range of different omni-directional units available which can be used for differing scanning applications, ranging from retail type applications with the barcodes read only a few centimeters away from the scanner to industrial conveyor scanning where the unit can be a couple of meters away or more from the code. Omni-directional scanners are also better at reading poorly printed, wrinkled, or even torn barcodes. Regular laser barcode readers may also include design features to allow reading of awkwardly presented barcodes.
While cell phone cameras without auto-focus are not ideal for reading some common barcode formats, there are 2D barcodes (such as Semacode) which are optimized for cell phones, as well as QR Codes and Data Matrix codes which can be read quickly and accurately with or without auto-focus.
The reader packaging can be distinguished as follows:
The handheld scanner with a handle and typically a trigger button for switching on the light source.
Pen scanner (or wand scanner) a pen-shaped scanner that is swiped.
A stationary scanner is a wall- or table-mounted scanner under or beside which the barcode is passed. These are commonly found at the checkout counters of supermarkets and other retailers.
A fixed-position scanner is an industrial barcode reader used to identify products during manufacture or logistics. Such is often used on conveyor tracks to identify cartons or pallets which need to be routed to another process or shipping location. Another application joins holographic (or barcode) scanners with a checkweigher to read bar codes of any orientation or placement, and weighs the package. Systems like this are used in factory and farm automation for quality management and shipping.
A PDA scanner (or Auto-ID PDA) is a PDA with a built-in barcode reader or attached barcode scanner.
An automatic reader is back office equipment to read barcoded documents at high speed (50,000/hour).
A cordless scanner (or Wireless scanner) is a cordless barcode scanner operated by a battery fitted inside it and is not connected to the electricity mains.
Methods of Connection
Early Serial Interfaces
Early barcode scanners, of all formats, almost universally used the then-common RS232 serial interface. This was an electrically simple means of connection and the software to access it is also relatively simple, although needing to be written for specific computers and their serial ports. There are a few less common proprietary interfaces as well
With the popularity of the PC and its standard keyboard interface, it became ever easier to connect physical hardware to a PC and so there was commercial demand similarly to reduce the complexity of the associated software. “Keyboard wedge” hardware plugged between the PC and its normal keyboard, allowed characters from the barcode scanner to appear exactly as if they had been typed at the keyboard. This made the addition of simple barcode reading abilities to existing programs very easy, without any need to change them, although it did require some care by the user and could be restrictive in the content of the barcodes that could be handled.
USB
Later barcode readers began to use USB connectors rather than the keyboard port, as this became a more convenient hardware option. To retain the easy integration with existing programs, a device driver called a “software wedge” could be used, to emulate the keyboard-impersonating behaviour of the old keyboard wedge hardware.
In many cases a choice of USB interface types (HID, CDC) are provided. Some have Powered USB.
Wireless Networking
Modern handheld barcode readers are operated in wireless networks according to IEEE 802.11g (WLAN) or IEEE 802.15.3 (Bluetooth). However, such a configuration limits the time of operation from a battery or rechargeable battery and requires recharging at least after a shift of operation.
Resolution
The scanner resolution is measured by the size of the dot of light emitted by the reader. If the dot of light is wider than any bar or space in the bar code, then it will overlap two elements (two spaces or two bars) and it may produce a wrong output. On the other hand, if a too small dot of light is used, then it can misinterpret any spot on the bar code making the final output wrong.
The most commonly used dimension is 13 mils (0.33 mm), although some scanners can read codes with dimensions as small as 3 mils (0.076 mm). Smaller bar codes are printed at high resolution to be read accurately.
In general, stationary scanners are used in point of sale systems. These have the advantage of being best able to read unclear or not well attached bar codes, and leave the operator's hands free to handle goods. On the other hand stationary scanners are expensive and take up large amounts of space. Handheld scanners do not take up space but interfere with the ability of the operator to handle the goods that are being scanned.